High density optical disk, apparartus for reproducing optical disk and method for producing optical disk master

ABSTRACT

An optical disk includes at least one region along a radial direction, and a plurality of tracks provided in the at least one region. The at least one region contains address regions radially positioned on the plurality of tracks. In the address regions, data which is common between two adjacent tracks of the plurality of tracks is recorded at positions aligned along the same radial direction on the two adjacent tracks, and data which is not common between the two adjacent tracks is recorded at positions along different radial directions on the two adjacent tracks.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical disk from/onto whichdata is reproduced/recorded by utilizing laser light; an optical diskapparatus which reads out or records signals using an optical disk; anda method for producing an optical disk master.

[0003] 2. Description of the Related Art

[0004] In recent years, an optical disk has been widely used as a mediumfor storing mass data files such as music, an image, and the like.Studies for increasing the capacity of an optical disk have been made inorder to realize a wider range for its use.

[0005] At present, due to the partial response technique, a recordingdensity of an optical disk apparatus is about 0.4 μm/bit in a lineardensity direction, and about 1.2 μm/track.

[0006] In order to realize a higher density optical disk, variousmethods have been suggested. One of such methods is a super-resolutionreadout method in which a reproducing film of an optical disk has asuper-resolution reproducing effect (see U.S. Pat. No. 5,168,482). The“super-resolution reproducing effect” refers to high-resolutionreproduction wherein its resolution level exceeds the resolution levelfor collected light beam. Such high-resolution reproduction is realizedby using a reproducing film heated by a light beam collected onto anoptical disk medium, which has a function of generating a reproductionsignal in a region having a predetermined temperature. According to thesuper-resolution readout method, it is possible to reproduce a signal ata resolution level higher than the resolution of a light beam, which isdetermined by the wavelength of its light source and the aperture of itscollective lens. Thus, it is possible to realize a high-density opticaldisk apparatus. Specifically, according to the super-resolution readoutmethod, a recording density can be improved up to about 0.2 μm/bit in aliner density direction and about 0.6 μm/track.

[0007] In order to produce an optical disk according to thesuper-resolution readout method, it is necessary to preformat addresses(e.g., sector numbers or track numbers which are recorded in sectoridentification regions) by providing emboss pits on the disk. However,such emboss pits do not provide the super-resolution effect. As aresult, when an address is recorded in a narrow track pitch of about 0.6μm, errors are generated due to cross-talk from an adjacent track.Consequently, the address cannot be reproduced. In order to avoid such aproblem, an optical disk in which addresses are recorded so as not to beadjacent to each other between two adjacent tracks has been suggested(e.g., U.S. Pat. No. 5,422,874).

[0008] Such optical disks wherein addresses are previously recorded byemboss pits are made by producing a master first and making reproductionusing the master by means of injection or the like. Such a master isgenerally produced as follows. A photoresist film is formed on acircular glass substrate. A light beam such as an argon laser, kryptonlaser, or the like is collected onto the photoresist film while theglass substrate is being rotated in a precise manner. Portions of thephotoresist film such as the grooves or the pits, which are exposed tolight by the collected light, are photosensitized. Thereafter, thephotoresist film is developed, thereby obtaining a photoresist filmhaving a predetermined pattern (i.e., grooves or pits). Using thethus-obtained photoresist film as a mask, the glass substrate is etchedso as to form grooves, emboss pits, and the like on the surface of theglass substrate. Next, the resist film is removed, and the surface ofthe glass substrate is then made to be conductive. Finally,electrodeposition of nickel or the like is performed for the conductiveglass substrate. In the manner as described above, the optical diskmaster is produced.

[0009] In recent years, upon producing a high density master, anelectron beam is often used instead of a light beam.

[0010] According to the optical disk disclosed in U.S. Pat. No.5,422,874, address regions are positioned along respectively differentradial directions between adjacent two tracks in order to realize anarrow track pitch. Therefore, the address region is required to have alength twice as long as the actually used data length of the addressregion at the expense of the capacity of the optical disk.

[0011] According to an optical disk wherein a data recording region isformed of a groove or a land (e.g., the optical disk disclosed in U.S.Pat. No. 5,422,874), it is extremely difficult to produce a masterthereof. Specifically, in order to improve reproduction characteristicsof emboss pits of address regions, each of the emboss pits needs to havea width of about 0.3 to about 0.4 μm. On the other hand, a groove regionserving as data recording region needs to have a width of about 0.6 toabout 0.7 μm which is about the same as the track pitch in order toequalize the reproduction characteristics at the groove region with thatat the land region. According to the conventional method for producingan optical disk master, however, since the master is generally producedusing one light beam or one electron beam, the width of the regionexposed to light, which corresponds to the line width of such a beam, isconstant. Therefore, it is extremely difficult to change the width of anaddress region from the width of a groove region.

[0012] In order to make the width of the address region and the width ofthe groove region different from each other, a method using two lightbeams having respectively different spot diameters has been known.However, in the case where a master is produced using two light beams,it is necessary to perform the alignment of the two light beams havingdifferent widths at an accuracy of about 0.1 μm or less. Thus, theproduction of the master is extremely difficult. Moreover, the width ofthe groove region on the master can only be made, at most, about 1.5times as large as that of the address region.

SUMMARY OF THE INVENTION

[0013] An optical disk of this invention may have one region or may beconcentrically divided into two or more regions, each of which includesa plurality of tracks. The plurality of tracks are further divided intoa plurality of regions along radial directions. Addresses radiallydisposed along the tracks constitute address regions formed on thetracks. According to data arrangement of the address regions, data whichis common between a first track and a second track adjacent to eachother is recorded at positions aligned along a radial direction, anddata which is different from each other between the first track and thesecond track is recorded at respectively different positions in a radialdirection. With the optical disk having such a structure, theabove-described problems can be solved.

[0014] A data region of the first track may be a groove, and a datarecording region of the second track may be a land portion.

[0015] The optical disk reproducing apparatus according to the presentinvention reproduces an optical disk wherein a polarity of a signal usedfor tracking the first and the second tracks is inverted between thefirst track and the second track. The apparatus for reproducing such anoptical disk includes a detector for detecting positional information ofthe address data in the address regions related to the first and thesecond tracks, and determining section for determining the polarity of asignal used for tracking based on information from the detector. Withthe apparatus having such a structure, the above-described problems canbe solved.

[0016] The apparatus for reproducing an optical disk includes an addresserror detector corresponding to the first track and the second track.The apparatus may use information from the address error detector asinformation for determining the tracking polarity of the data regions ofthe first track and the second track.

[0017] According to one aspect of this invention, an optical diskincludes at least one region along a radial direction, and a pluralityof tracks provided in the at least one region. The at least one regioncontains address regions radially positioned on the plurality of tracks.In the address regions, data which is common between two adjacent tracksof the plurality of tracks is recorded at positions aligned along thesame radial direction on the two adjacent tracks, and data which is notcommon between the two adjacent tracks is recorded at positions alongdifferent radial directions on the two adjacent tracks.

[0018] In one embodiment of the present invention, the plurality oftracks include a plurality of first tracks and a plurality of secondtracks in which the address region includes the data which is commonbetween the plurality of first tracks and the plurality of second tracksat a position along the same radial direction, and includes the datawhich is not common between the plurality of first tracks and theplurality of second tracks at positions along different radialdirections. Each of the plurality of first tracks and each of theplurality of second tracks are alternately repeated.

[0019] In another embodiment of the present invention, the at least oneregion further includes a data recording region which is different fromthe address regions; and each of the plurality of first tracks in thedata recording region is formed of a groove, and each of the pluralityof second tracks in the data recording region is formed in a regionbetween the grooves of two adjacent tracks of the plurality of firsttracks.

[0020] In still another embodiment of the present invention, of theaddress regions positioned on the plurality of second tracks, each ofthe plurality of first tracks in the address region, where data which isdifferent from each other between the plurality of first tracks and theplurality of second tracks is recorded, is formed of a groove.

[0021] According to another aspect of this invention, an apparatusreproduces data recorded in an optical disk having at least one regionalong a radial direction, and a plurality of tracks provided in the atleast one region. The optical disk includes address regions radiallypositioned on the plurality of tracks provided in the at least oneregion. In the address regions, data which is common between twoadjacent tracks of the plurality of tracks is recorded at positionsaligned along the same radial direction on the two adjacent tracks, anddata which is not common between the two adjacent tracks is recorded atpositions along different radial directions on the two adjacent tracks;and a tracking polarity is changed at least one point in the twoadjacent tracks. The apparatus includes: a detecting section fordetecting record positions of data recorded in the address regions inthe two adjacent tracks; and a determining section for determining atracking polarity of a track being reproduced among the plurality oftracks based on an output from the detecting section.

[0022] In one embodiment of the present invention, the detecting sectionis an error detector for detecting error information in data recorded inthe address regions so as to correspond to each of the two adjacenttracks; and the record position of the data is detected based on thedetection of the error information for the data.

[0023] According to still another aspect of this invention, a method forproducing an optical disk master includes the steps of: (a) providing asubstrate having a photoresist film provided on a surface thereof; (b)rotating the substrate in a relative relationship with a beam; (c)irradiating the photoresist film on the substrate with the beam so as toform a first beam trace in the photoresist film; (d) further irradiatingthe photoresist film with the beam such that the beam partially overlapsthe first beam trace, so that a second beam trace is formed in thephotoresist film; and (e) completing the optical disk master using thephotoresist film.

[0024] In one embodiment of the present invention, the step (d)comprises shifting the beam in a radial direction of the substrate andirradiating the photoresist film with the beam so as to form the secondbeam trace.

[0025] In another embodiment of the present invention, the step (d)includes formation of a second beam trace having a width which is largerthan a half-value of the width of the beam in the photoresist film.

[0026] Thus, the invention described herein makes possible theadvantages of (1) providing an optical disk having an improved recordingdensity efficiency, and (2) providing a method for easily producing anoptical disk master in which a width of each of emboss pits of addressregions and a width of a groove region are different from each otherusing a light beam having a constant spot diameter.

[0027] These and other advantages of the present invention will becomeapparent to those skilled in the art upon reading and understanding thefollowing detailed description with reference to the accompanyingfigures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIGS. 1A and 1B are views for illustrating the structures of anoptical disk 100 and an address number region 105-1 thereof according toExample 1 of the present invention;

[0029]FIG. 2 is a view for illustrating the structure of an addressnumber region 105-2 of an optical disk according to Example 2 of thepresent invention;

[0030]FIGS. 3A to 3C are views for illustrating structures of an opticaldisk 200, and address number regions 205 and 207 according to Example 3of the present invention;

[0031]FIG. 4 shows the optical disk 200 having a structure whereingroove regions change to land regions at a part of the disk according toExample 3 of the present invention;

[0032]FIG. 5 is a block diagram showing a device 350 for determiningtracking position according to Example 3 of the present invention; and

[0033]FIGS. 6A to 6C are views for showing a part of an optical diskmaster produced according to Example 4 of the present invention, and thesteps for producing the master.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] Hereinafter, the present invention will be described by way ofillustrative, but non-limiting examples with reference to theaccompanying drawings. The same components are denoted by the samereference numerals in the following examples.

EXAMPLE 1

[0035]FIG. 1A shows the structure of an optical disk 100 according toExample 1 of the present invention.

[0036] The optical disk 100 includes: a first zone 101 and a second zone102, which are obtained by concentrically dividing the optical disk 100;sectors 103 obtained by dividing the first zone 101 into 12 sectionsalong radial directions; sectors 104 which are obtained by dividing thesecond zone 102 into 16 sections along radial directions; address numberregions 105-1 of the sectors 104 which are recorded by pits; and datarecording regions 106 which record data of the sectors 104.

[0037] Although the optical disk 100 is concentrically divided into thefirst zone 101 and the second zone 102 in Example 1 of the presentinvention, the optical disk 100 may be divided into three or more zones.

[0038] Each of the first zone 101 and the second zone 102 is dividedinto sectors so that linear densities for tracks of the disk 100 arenearly the same. According to Examples of this invention described inthis specification, the first zone 101 includes 12 sectors 103, thesecond zone 102 includes 16 sectors. However, conditions for dividingthe first zone 101 and the second zone 102 into sectors are not limitedthereto. The first zone 101 and the second zone 102 may be divided intosectors in accordance with other suitable conditions.

[0039] According to Example 1 and each of the later-described examplesof the present invention, only sectors 104 along the outer periphery ofthe disk are mentioned upon describing the present invention. However,the present invention can be applied to the sectors 103 along the innerperiphery of the disk in the same manner as in the sectors 104.

[0040]FIG. 1B shows the structures of the address number region 105-1and the data recording region 106.

[0041] The address number region 105-1 includes: an address mark region107 in which address marks for identifying the start points of addressnumbers are recorded; a sector number region 108 in which sector numbersare recorded; a first track number region 109 in which track numbers forgroove tracks 111 are recorded; a second track number region 110 whereintrack numbers for land tracks 112, each of which is interposed betweenthe groove tracks 111, are recorded.

[0042] According to the optical disk 100 of Example 1, address marks andsector numbers between the adjacent tracks in one sector arerespectively recorded at positions aligned along a radial direction ofthe optical disk 100. Specifically, the address marks are recorded inthe address mark region 107, and the sector numbers are recorded in thesector number region 108. As to data recorded in the address mark region107 and data recorded in the sector number region 108, a common value isassigned between the two adjacent tracks.

[0043] Track numbers can take different values between the two adjacenttracks. Track numbers are divided into track numbers at the time ofgroove tracking and track number at the time of land tracking. The thusdivided track numbers are respectively recorded to the first tracknumber region 109 and the second track number region 110 so that theyare not adjacent to each other between adjacent tracks.

[0044] The data recording region 106 is created by the spiral groovetracks 111 used for tracking, and the land tracks 112, each of which isinterposed between the groove tracks 111. Data to be recorded isrecorded on the groove track 111 and the land track 112.

[0045] According to Example 1 of the present invention, a width of thegroove 111 is set to be about 0.7 μm, and a width between grooves 111,i.e., a width of the land region, is set to be about 0.7 μm. Accordingto the super-resolution readout method, even with such an extremelynarrow track pitch, cross-talk from the adjacent track is greatlyreduced in the data recording region 106. Therefore, it is possible toread out or write data at a low error rate.

[0046] In the sector number region 108, the first track number region109, and the second track number region 110 in the address number region105-1, data is recorded according to bi-phase modulation in which “1” isrepresented as “10” and “0” is represented as “01”. In the address markregion 107, code 111000, which does not appear in the bi-phasemodulation, is recorded as an address mark.

[0047] Since data in the address number region 105-1 is recorded as pitsutilizing emboss pits of the disk, it is impossible to obtainsuper-resolution effect of the disk. Moreover, cross-talk may begenerated. Thus, there is a possibility of not being able to reproducedata recorded in the address mark region 107 and the sector numberregion 108.

[0048] According to the aforementioned data configuration, however, evenwhen cross-talk is generated as a result of not being able to obtain thesuper-resolution effect, address marks and sector numbers respectivelyrecorded in the address mark region 107 and the sector number region 108can be reproduced. This is because an interfering signal due to thecross-talk is the same as a track signal to be read out. Accordingly,the optical disk receives no influence from cross-talk. Thus, readingerrors are not caused by cross-talk.

[0049] Both of address marks and sector numbers are recorded on theoptical disk 100 so as to be adjacent to each other between the adjacenttracks, regardless of whether they are data for groove track 111 or datafor land track 112. Therefore, as compared to the case where all piecesof address information in each of tracks are recorded so as not to beadjacent to each other, data length of the address number region 105-1can be reduced by an amount equal to the length of data regions in theaddress mark region 107 and the sector number region 108. In otherwords, the capacity of the optical disk can be effectively utilized.

[0050] Track numbers for tracks positioned adjacent to each other arerecorded in an alternate manner in the track number regions 109 and 110on the optical disk 100 so as not to be adjacent to each other betweentwo adjacent tracks depending on whether it is the track number for thegroove track 111 or the track number for the land track 112. Thus, apitch of the track in which a track number is recorded becomes twice aslong as the track pitch of the address mark region 107 or the sectornumber region 108. As a result, cross-talk from the neighboring track issignificantly reduced.

[0051] Although address marks and sector numbers can have common values,respectively, between adjacent tracks according to Example 1 of thepresent invention, kinds of data which can take a common value betweenadjacent tracks are not limited thereto. Even with data other thanaddress marks and sector numbers, data which is common between adjacenttracks and data which is not common between adjacent tracks is recordedseparately according to the optical disk of the present invention.Consequently, as compared to the conventional optical disk, the addressnumber region 105-1 in the optical disk of this invention can bestructured more efficiently and at an extremely low error rate.

[0052] In Example 1 of the present invention, a track number which isrecorded in the first track number region 109 represents the tracknumber for groove track 111, and a track number which is recorded in thesecond track number region 110 represents the track number for landtrack 112. However, track numbers in the first track number region 109may represent track numbers for land tracks 112, and track numbers inthe second track number region 110 may represent track numbers forgroove tracks 111.

[0053] In each of the examples described hereinafter, the order of theregion in which track numbers for groove tracks are recorded and theregion in which track numbers for land tracks are recorded is notlimited to the illustrated order.

EXAMPLE 2

[0054] In Example 1 of the present invention, even when a land region inthe second track number region 110 (see FIG. 1B) is tracked, the addresspits in the second track number region 110 serve as partial grooves. Asa result, a large level of disturbance is caused in a tracking errorsignal.

[0055] In order to avoid an off-track phenomenon resulting from suchdisturbance, it is necessary to hold the tracking servo upon reading thesecond track number region according to the optical disk of Example 1.

[0056] An optical disk according to Example 2 of the present inventionhas the same structure as that of the optical disk described in Example1 except for the structure of the track number region 110 (FIG. 1B) atthe time of land tracking, which is included in the address numberregion 105-1 (FIG. 1B). Therefore, description regarding the structuresother than that of the track number region are herein omitted.

[0057]FIG. 2 shows the structure of an address number region 105-2 inthe optical disk according to Example 2 of the present invention.

[0058] A track number region 114 which contains track numbers for theland tracks 112 includes a plurality of pits representing land tracknumbers on the land tracks. A groove 116 is formed on a track in which aplurality of pits in the track number region 114 are not formed.

[0059] An optical disk generally performs tracking of a land regionutilizing an edge of the adjacent groove region. Therefore, it becomespossible to perform stable tracking of the land region by providing thegroove 116. In other words, the level of disturbance at the time oftracking can be greatly reduced. As a result, it is no longer necessaryto hold the tracking servo, which is required upon reproducing theoptical disk of Example 1. Accordingly, by providing the groove 116,tracking can be stably performed even when the groove track 116 in thefirst track number region 109 and the data recording region 106 arereproduced.

EXAMPLE 3

[0060]FIG. 3A shows the structure of an optical disk 200 according toExample 3 of the present invention.

[0061] The optical disk 200 includes: a first zone 201 and a second zone202, which are obtained by concentrically dividing the optical disk 200;sectors 203 obtained by dividing the first zone 201 into 12 sectionsalong radial directions; sectors 204 which are obtained by dividing thesecond zone 202 into 16 sections along radial directions; address numberregions 205 in the sectors 204, which are recorded by pits; datarecording regions 206, in which data for the sectors 204 are recorded;an address number region 207 where switching between land tracking andgroove tracking occurs; groove address regions 208 where track numbersand cyclic redundancy check (hereinafter, referred to simply as “CRC”)error codes of groove tracks in the address number region 205 or 207 arerecorded; and land address regions 209 where track numbers and CRC errorcodes of land tracks in the address number region 205 or 207 arerecorded. A CRC error code is information used for detecting errorswhich occur while information recorded in an optical disk is read out.

[0062] Although the optical disk 200 is concentrically divided into thefirst zone 201 and the second zone 202 in Example 3 of the presentinvention, the optical disk 200 may be divided into three or more zones.

[0063] Each of the first zone 201 and the second zone 202 is dividedinto sectors so that linear densities for tracks of the disk 200 are thesame. However, conditions for dividing the first zone 201 and the secondzone 202 into sectors are not limited thereto. The first zone 201 andthe second zone 202 may be divided into sectors in accordance with othersuitable conditions.

[0064] According to the optical disk 100 (FIGS. 1A and 1B) of Example 1,since the shape of a groove in the data recording region is spiral, thegroove region and the land region are not connected to each other.Accordingly, in order to reproduce the groove region of the Nth trackand the land region of the (N+1)th track in a continuous manner, it isnecessary to move a light spot for reproduction from the groove regionto the land region, i.e., to perform a track jump.

[0065] According to the optical disk 200 of Example 3, however, a grooveregion change to a land region at a point in a track of the disk asshown in FIG. 4. Therefore, an optical disk 200 having such a structuremakes it possible to continuously reproduce the groove region and theland region of a track without performing a track jump. For example,immediately after reproduction for the groove region of the Nth track iscompleted, reproduction for the land region of the (N+1)th trackautomatically begins without performing a track jump.

[0066] Next, data arrangement for the optical disk 200 having thestructure as shown in FIG. 4 will be described with reference to FIGS.3B and 3C.

[0067]FIG. 3B shows the address number region 207 in the sector 204,where switching between groove region and land region is performed.

[0068] The address number region 207 includes: an address mark region; asector number region; the groove address region 208; and the landaddress region 209. The address mark region and the sector number regionin this example have the same structures as those of the address markregion and the sector number region described in Example 1.Specifically, address marks and sector numbers between the adjacenttracks are respectively recorded at positions aligned along a radialdirection of the optical disk 200.

[0069] Each of the groove address region 208 and the land address region209 includes track numbers and CRC error codes. Since track numbers andCRC error codes can take different values between adjacent tracks,respectively, the groove address region 208 and the land address region209 are located on the optical disk 200 so as not to be adjacent to eachother between adjacent tracks. As explained in Example 1 of the presentinvention, cross-talk can be avoided by such an arrangement.

[0070] Such address data, i.e., track numbers and CRC error codes, isrecorded as follows. Address data for a groove track in the datarecording region 206 is recorded in the groove address region 208. Onthe other hand, address data for a land track in the data recordingregion 206 is recorded in the land address region 209. Specifically, fora groove track in the data recording region 206 positioned next to theaddress number region 207, a track number and a CRC error code arerecorded in the groove address region 208 in the address number region207. At this time, the land address region 209 is blank. For a landtrack in the data recording region 206 positioned next to the addressnumber region 207, a track number and a CRC error code are recorded inthe land address region 209 in the address number region 207. At thistime, the groove address region 208 is blank.

[0071] The address number region 205 shown in FIG. 3C is the addressnumber region in the sector 204, where switching between a groove regionand a land region is not performed. Address data included in the addressnumber region 205 is recorded in the same manner as that describedabove. Specifically, address data for a groove track in the datarecording region 206 is recorded in the groove address region 208, andaddress data for a land track in the data recording region 206 isrecorded in the land address region 209.

[0072] Hereinafter, the case where the point at which a groove region isswitched to a land region on the optical disk 200 of this example isreproduced, or the case where the point at which a land region isswitched to a groove region is reproduced will be described.

[0073] Reproducing a groove region and a land region continuouslywithout performing a track jump indicates that tracking polarity (i.e.,position) changes from land to groove, or groove to land, with theaddress number region 207 serving as a boundary. Such a change intracking polarity (i.e., position) may occur at a point or a pluralityof points in two adjacent tracks. By detecting such a change in trackingpolarity or position, it is possible to determine whether the datarecording region 206 positioned next to the address number region 207corresponds to a groove region or land region.

[0074] A recording position for a track number and a CRC error code isdetermined in accordance with tracking position in the data recordingregion 206 which comes after the address number region 207.

[0075] By recording optical disk track numbers and CRC error codes inthe address number region 207 as described above, it is possible todetermine tracking position in the data recording region 206, usingerror information read out from the address number region 207.

[0076] Hereinafter, a method for determining tracking position will bedescribed with reference to FIG. 5.

[0077]FIG. 5 is a block diagram showing the structure of a device 350for determining tracking position (hereinafter, referred to as “trackingposition determining device”) in an apparatus for reproducing an opticaldisk according to Example 3 of the present invention. The trackingposition determining device 350 is included in the apparatus forreproducing an optical disk.

[0078] The tracking position determining device 350 includes: addressdemodulators 301 and 302 for demodulating data recorded in the grooveaddress region 208 and the land address region 209 shown in FIG. 3,respectively; sections 303 and 304 for determining CRC errors of datademodulated in the address demodulators 301 and 302, respectively(hereinafter, referred to as “error determining sections”); and ANDgates 305 to 307.

[0079] The address demodulators 301 and 302 demodulate address datawhich is read out. The error determining sections 303 and 304 output “1”when no address demodulation error occurs, and output “0” when addressdemodulation error occurs. The error determining sections 303 and 304make a determination regarding the occurrence of an error using a CRCerror code as described above. Such a determination entails determiningwhether a CRC error code is recorded in a region of the track presentlybeing reproduced and as to which area of the track the CRC error code isrecorded in. Therefore, the error determining sections 303 and 304 areused for detecting the record position of a CRC error code. The ANDgates 305 to 307 receive determination results from the errordetermining sections 303 and 304, and output a signal indicating one ofthe following three cases: the read address data is address data whichperforms groove tracking; the read address data is address data whichperforms land tracking; and reproduction error. Based on the output, asection for determining the tracking position (not shown) in the opticaldisk reproducing apparatus determines the tracking position of the trackpresently being reproduced.

[0080] Hereinafter, the case where the Nth track and the (N+1)th trackin the address number region 205 (FIG. 3C) are reproduced using theaddress demodulators 301 and 302 will be described.

[0081] As to the Nth track in the address number region 205 (FIG. 3C), atrack number and a CRC error code are recorded in the groove addressregion 208 (FIG. 3C). In this case, the output of the error determiningsection 303 becomes 1, and the output of the error determining section304 becomes 0. Then, a signal indicating groove tracking is output bythe AND gate 305. As a result, the reproducing apparatus which isreproducing the groove region at that time determines that thesubsequent reproduction position is also in groove region, based on thesignal indicating groove tracking which is output from the trackingposition determining device 350.

[0082] As to the (N+1)th track in the address number region 205 (FIG.3C), a track number and a CRC error code are recorded in the landaddress region 209 (FIG. 3C). In this case, the output of the errordetermining section 303 becomes 0, and the output of the errordetermining section 304 becomes 1. Then, a signal indicating landtracking is output by the AND gate 306. As a result, the reproducingapparatus which is reproducing the land region at that time determinesthat the subsequent reproduction position is also in land region, basedon the signal indicating land tracking which is output from the trackingposition determining device 350.

[0083] In the case where the address number region 205 has defects, andboth of the error determining sections 303 and 304 thereby indicate anerror, the output of the AND gate 307 becomes 1, and a signal indicatingaddress demodulation error is output. When address demodulation erroroccurs, the reproducing apparatus determines tracking position using thesector number of the sector previously reproduced and the sector numberfor the zone of the present tracking position, and determines that thesubsequent reproduction position is in a groove region or a land region.

[0084] Next, the case where the Nth track and the (N+1)th track in theaddress number region 207 (FIG. 3B) are reproduced using the addressdemodulators 301 and 302 will be described.

[0085] The Nth track in the address number region 207 (FIG. 3B) changesfrom a groove track to a land track around the address number region 207(FIG. 3B).

[0086] As to the Nth track in the address number region 207 (FIG. 3B), atrack number and a CRC error code are recorded in the land addressregion 209 (FIG. 3B). In this case, the output of the error determiningsection 303 becomes 0, and the output of the error determining section304 becomes 1. Then, a signal indicating land tracking is output by theAND gate 306. As a result, the reproducing apparatus which isreproducing the groove region at that time determines that thesubsequent reproduction position corresponds to a land region, based onthe signal indicating land tracking which is output from the trackingposition determining device 350.

[0087] As to the (N+1)th track in the address number region 207 (FIG.3B), a track number and a CRC error code are recorded in the grooveaddress region 208 (FIG. 3B). In this case, the output of the errordetermining section 303 becomes 1, and the output of the errordetermining section 304 becomes 0. Then, a signal indicating groovetracking is output by the AND gate 305. As a result, the reproducingapparatus which is reproducing the land region at that time determinesthat the subsequent reproduction position corresponds to a grooveregion, based on the signal indicating groove tracking which is outputfrom the tracking position determining device 350.

[0088] As described above, by changing format in the address recordingregion depending on whether the position to be reproduced nextcorresponds to groove region or land region, it is possible to easilydetect tracking position to be reproduced next even when trackingposition changes from groove region to land region, or from land regionto groove region.

EXAMPLE 4

[0089] In Example 4 of the present invention, a method for producing amaster for optical disks such as the optical disks described in Examples1 to 3 of the present invention will be described.

[0090] In terms of reproduction characteristics, it is most preferablethat a pit width in the address number region 105-1 (FIG. 1B) of theoptical disk 100 (FIG. 1A) is in the range of about 0.3 to about 0.4 μm,and a width of a groove used for tracking in the data recording regionis about 0.7 μm which is the same value as the track pitch. Hereinafter,a method for producing an optical disk master 400 according to thisinvention, which has the above-described pitch width and groove widthwill be described with reference to FIGS. 6A, 6B, and 6C.

[0091]FIG. 6A shows the structure of a part of the optical disk master400 which is produced according to the method for producing an opticaldisk master of Example 4.

[0092] The optical disk master 400 includes: groove regions 401 whichare data recording regions; a common address data region 402 containingaddress marks, sector numbers, and the like; a first uncommon dataregion 403 containing groove track numbers and the like; a seconduncommon data region 404 containing land track numbers and the like;deformed portions 406 of the groove regions resulting from deformationin parts of the groove regions; and land regions 405 which are datarecording regions. Each groove region 401 and each land region 405constitute a track 407.

[0093] Hereinafter, the method for producing the master having thepattern shown in FIG. 6A will be described with reference to FIGS. 6Band 6C. As to FIGS. 6B and 6C, production of the master is performed inthe order from the left side in the figures towards the right side. Asto FIG. 6A, production of tracks 407 is performed in the order from thetop side in the figure towards the bottom side.

[0094] In order to simplify the description for the method for producingthe master, the description will start with the state where aphotoresist film is formed on a circular glass substrate in Example 4 ofthe present invention. In order to form the photoresist film on thecircular glass substrate, any well known method may be used. The term“cutting” as used herein refers to the formation of a mark region or aportion to be a groove later in the photoresist film formed on thecircular glass substrate during the production of the optical diskmaster.

[0095]FIG. 6B shows the state where cutting of the photoresist film isperformed using light beam during the first rotation of the substrate.Cut portions are indicated by halftone dots.

[0096] A part of the groove region 401 is cut by irradiation of lightbeam which is displaced from the center line of the track 407 by anamount of P.

[0097] Next, the amount of light beam displacement P is set to be zero,and cutting of the common data region 402 and the first uncommon dataregion 403 is performed.

[0098] Thereafter, cutting of the groove region 401 is performed againby means of irradiation of light beam which is displaced from the centerline of the track 407 by an amount of P. The cutting of the deformedportion 406 of the groove region can be realized by increasing thedisplacement amount P regarding irradiation position of light beam.

[0099] By changing the displacement amount P during the first rotationof the substrate as described above, a pit and a part of a groove iscut.

[0100]FIG. 6C shows the state where cutting of the photoresist film isperformed using light beam during the second rotation of the substrate.Cut portions are denoted by the hatched portions.

[0101] During the second rotation of the substrate, the groove region401, which has been partially cut during the first rotation of thesubstrate, is further cut.

[0102] Light beam irradiation position during the second rotation of thesubstrate is shifted toward a direction closer to the desired cutportion of the groove region 401, from the center of the track followingthe track which has been cut during the first rotation of the substrate,by an amount of Q. At this time, the groove portion 401 is cut so thatthe cut portion during the second rotation of the substrate partiallyoverlaps the cut portion during the first rotation of the substrate.

[0103] Next, the amount of light beam displacement Q is set to be zero,and cutting of the common data region 402 and the second uncommon dataregion 404 is performed. The cutting of the deformed portion 406 of thegroove region can be realized by setting the aforementioned displacementamount Q to be a smaller value. At this time, the deformed portion 406of the groove region is cut so that a light beam trace during the secondrotation of the substrate partially overlaps the light beam trace duringthe first rotation of the substrate.

[0104] After the cutting is completed, it is possible to produce theoptical disk master using the photoresist film in which light beamtraces are formed. Since the following steps up until the completedmaster is obtained are the same as those already known in the art, thedescription thereof is herein omitted.

[0105] According to the above-described cutting method, cutting of anyposition, or a mark region or a groove region 401 of any shape can beperformed by shifting a light beam or an electron beam in a radialdirection at any position on the substrate so that the light beam traceduring the first rotation of the substrate partially overlaps the lightbeam trace during the second rotation of the substrate.

[0106] For example, a desired portion of a large mark region (i.e., thecommon data region 402 and the uncommon data regions 403 and 404) or thegroove region 401, which has a width greater than the half-value widthof a light beam, can be cut so as to produce an optical disk master.

[0107] For example, it is possible to easily produce an optical diskmaster in which a width of each of the emboss pits of address regionsand a width of a groove region have different values.

[0108] Even with the conventional master producing apparatus using twolight beams, it is difficult to form the deformed portion 406 having agroove width different from that of the groove region 401 in a part ofthe groove region 401. According to the method for producing an opticaldisk master in Example 4 of the present invention, however, the deformedportion 406 of the groove region 401 can be easily produced simply bychanging the running position of a light beam. This is because it isrelatively easy to control the running position of one light beam at a0.1 μm level or less. By using the above-described method, the need forusing an expensive master producing apparatus, having two light beams,is eliminated.

[0109] Example 4 of the present invention describes the case wherecutting is performed without changing the intensity of a light beam.However, by changing the intensity of the light beam as necessary, thewidth of the mark region and the width of the groove region 401 can bevaried more flexibly. More specifically, the width of the groove regioncan be made about three times as large as the width of the mark region.

[0110] According to the description above, the light beam irradiates therotating glass substrate. However, this is only one example whereincutting is performed by relative movement of a light beam and glasssubstrate. The present invention is not limited to the case where theglass substrate rotates. For example, the glass substrate may be fixedand irradiated with a rotating light beam.

[0111] Although a light beam irradiates the rotating glass substrate inExample 4 of the present invention, any beam can be used as long as thephotoresist film is exposed by the beam. For example, an electron beamor the like can be used.

[0112] According to the optical disk of the present invention, datawhich is common between two adjacent tracks of the plurality of tracksis recorded at positions aligned along the same radial direction on thetwo adjacent tracks, and data which is not common between two adjacenttracks is recorded at positions along different radial directions on thetwo adjacent tracks. Accordingly the recording density efficiency isimproved.

[0113] Moreover, errors caused by cross-talk can be avoided. Thus, it ispossible to realize a high density disk with an address region having ahigh efficiency and a low error rate.

[0114] According to the present invention, it is possible to detect thetracking position of a track being reproduced, based on predeterminedinformation recording in the track. Therefore, according to the presentinvention, upon reproducing the optical disk having a structure suchthat groove regions change to land regions at a part of the disk, it ispossible to easily detect the tracking polarity position to bereproduced next even when the tracking polarity (i.e, position) changesfrom a groove region to a land region, or from a land region to a grooveregion.

[0115] According to the method for producing an optical disk master ofthis invention, since groove region on the optical disk master is formedby two substrate rotation processes, it is possible to easily produce,using one light beam, a master in which the width of each of emboss pitsof the address regions and the width of the groove region are differentfrom each other.

[0116] According to the method for producing an optical disk master ofthis invention, the deformed portion of the groove region can be easilyformed simply by changing the running position of a light beam.

[0117] According to the method for producing an optical disk master ofthis invention, as compared to the method in which a groove of a widewidth is formed simply by performing power control of one beam, it ispossible to suppress formation of a blunt edge in the groove, and tochange a range of a groove width.

[0118] Various other modifications will be apparent to and can bereadily made by those skilled in the art without departing from thescope and spirit of this invention. Accordingly, it is not intended thatthe scope of the claims appended hereto be limited to the description asset forth herein, but rather that the claims be broadly construed.

What is claimed is:
 1. An optical disk comprising at least one regionalong a radial direction, and a plurality of tracks provided in the atleast one region, wherein the at least one region contains addressregions radially positioned on the plurality of tracks; and wherein inthe address regions, data which is common between two adjacent tracks ofthe plurality of tracks is recorded at positions aligned along the sameradial direction on the two adjacent tracks, and data which is notcommon between the two adjacent tracks is recorded at positions alongdifferent radial directions on the two adjacent tracks.
 2. An opticaldisk according to claim 1 , wherein the plurality of tracks include aplurality of first tracks and a plurality of second tracks in which theaddress region includes the data which is common between the pluralityof first tracks and the plurality of second tracks at a position alongthe same radial direction, and includes the data which is not commonbetween the plurality of first tracks and the plurality of second tracksat positions along different radial directions, wherein each of theplurality of first tracks and each of the plurality of second tracks arealternately repeated.
 3. An optical disk according to claim 2 , wherein:the at least one region further includes a data recording region whichis different from the address regions; and each of the plurality offirst tracks in the data recording region is formed of a groove, andeach of the plurality of second tracks in the data recording region isformed in a region between the grooves of two adjacent tracks of theplurality of first tracks.
 4. An optical disk according to claim 3 ,wherein of the address regions positioned on the plurality of secondtracks, each of the plurality of first tracks in the address region,where data which is different from each other between the plurality offirst tracks and the plurality of second tracks is recorded, is formedof a groove.
 5. An apparatus for reproducing data recorded in an opticaldisk having at least one region along a radial direction, and aplurality of tracks provided in the at least one region, the opticaldisk including address regions radially positioned on the plurality oftracks provided in the at least one region, wherein in the addressregions, data which is common between two adjacent tracks of theplurality of tracks is recorded at positions aligned along the sameradial direction on the two adjacent tracks, and data which is notcommon between the two adjacent tracks is recorded at positions alongdifferent radial directions on the two adjacent tracks; and a trackingpolarity is changed at least one point in the two adjacent tracks, theapparatus comprising: a detecting section for detecting record positionsof data recorded in the address regions in the two adjacent tracks; anda determining section for determining a tracking polarity of a trackbeing reproduced among the plurality of tracks based on an output fromthe detecting section.
 6. An apparatus according to claim 5 , wherein:the detecting section is an error detector for detecting errorinformation in data recorded in the address regions so as to correspondto each of the two adjacent tracks; and the record position of the datais detected based on the detection of the error information for thedata.
 7. A method for producing an optical disk master, comprising thesteps of: (a) providing a substrate having a photoresist film providedon a surface thereof; (b) rotating the substrate in a relativerelationship with a beam; (c) irradiating the photoresist film on thesubstrate with the beam so as to form a first beam trace in thephotoresist film; (d) further irradiating the photoresist film with thebeam such that the beam partially overlaps the first beam trace, so thata second beam trace is formed in the photoresist film; and (e)completing the optical disk master using the photoresist film.
 8. Amethod for producing an optical disk master according to claim 7 ,wherein the step (d) comprises shifting the beam in a radial directionof the substrate and irradiating the photoresist film with the beam soas to form the second beam trace.
 9. A method for producing an opticaldisk master according to claim 7 , wherein step (d) comprises formationof a second beam having a width which is larger than a half-value of thewidth of the beam in the photoresist film.